Best OTC Laxatives for Constipation in the US (Fast & Gentle Options)

Disclosure: This article contains affiliate links. If you purchase through our links, we may earn a small commission at no extra cost to you. Our rankings are based solely on clinical evidence — not affiliate relationships. 

---

Finding the best OTC laxatives for constipation is not as simple as grabbing the first box you see on a pharmacy shelf. With dozens of products claiming to work — from fiber powders to stimulant pills to stool softeners — most people end up choosing based on a brand name, a TV commercial, or a friend’s advice.

That’s a problem. Because not all laxatives work the same way, and some of the most popular options have almost no clinical evidence behind them.

Constipation affects roughly 16% of adults in the US, and over-the-counter laxatives are among the most frequently purchased products in any drugstore. Chronic idiopathic constipation (CIC) — long-term constipation with no clear underlying cause — affects roughly 8–12% of the US population. Many people try OTC options before seeing a doctor, but often end up choosing products that lack strong clinical support.

This guide cuts through the noise. We ranked every major OTC laxative using three authoritative sources:

• Rao & Brenner (2021): A landmark systematic review in the American Journal of Gastroenterology that screened 1,297 studies and analyzed 41 qualifying clinical trials from 2004–2020.
• AGA–ACG Clinical Practice Guideline (2023): The most up-to-date joint guideline from America’s two leading gastroenterology societies, using the gold-standard GRADE methodology.
• Mayo Clinic: For patient-friendly safety guidance and laxative categories.

By the end, you will know exactly which products have the strongest evidence, which ones to avoid, and how to choose the right option for your situation.

What Is Constipation? Simple Signs to Watch For

According to Mayo Clinic, constipation means you are having fewer bowel movements than usual, or your stools are hard, dry, and difficult to pass.³ Most doctors define constipation as fewer than three bowel movements per week.

Common symptoms include:

• Straining to pass stool
• Hard or lumpy stools
• Feeling like your bowel never completely empties
• Bloating and abdominal discomfort

Common causes include low fiber intake, inadequate fluid intake, physical inactivity, certain medications, and aging. Women experience constipation more often than men, and it becomes more common after age 60.

Before reaching for a laxative, Mayo Clinic recommends trying lifestyle changes first: eat 25–31 grams of fiber daily, drink 8–10 glasses of water per day, and exercise regularly.³ For more on how dehydration drives constipation, see our guide: Does Dehydration Cause Constipation?

How Do We Know Which Laxatives Work? Understanding the Evidence

Not all laxative claims are equal. The 2021 Rao & Brenner review graded each OTC treatment using a clear system:

Grade	What It Means	Plain English
Grade A	Good evidence from multiple well-designed trials	✅ Strongly recommended
Grade B	Moderate evidence; fewer or smaller trials	✅ Recommended
Grade C	Poor evidence from weak trials	⚠️ Not routinely recommended
Grade I	Not enough data to make any recommendation	❌ Insufficient evidence

The 2023 AGA–ACG Guideline used the GRADE system with two recommendation strengths:

• Strong recommendation — Most patients should use this. Benefits clearly outweigh risks.
• Conditional recommendation — A good option for many patients, but the decision should be made with your doctor based on your individual situation.

Important note on ranking: In the Quick Answer above, Bisacodyl is ranked #2 and Senna #3 — even though both received Grade A in the 2021 review. This is because the 2023 AGA–ACG Guideline gave Bisacodyl a strong recommendation, while Senna received only a conditional recommendation. Under the more rigorous GRADE framework, Bisacodyl’s evidence is considered more reliable for short-term use.

Best OTC Laxatives at a Glance: Full Comparison Table

1. MiraLAX (Polyethylene Glycol) — Best Overall OTC Laxative

🏆 Evidence Rating: Grade A (2021) | Strong Recommendation (2023 AGA–ACG)

What Is It and How Does It Work?

MiraLAX contains polyethylene glycol 3350 (PEG), an osmotic laxative. It works by drawing water into the colon, softening stool and making it easier to pass. According to Mayo Clinic, osmotic laxatives “draw water into the colon to allow easier passage of stool.”³ PEG is not absorbed by the body, so it stays in the gut and works locally — making it one of the safest options for regular use.

What Does the Research Say?

PEG is the most thoroughly studied OTC laxative available. In the 2021 systematic review, PEG received a Grade A recommendation — the highest possible rating — based on 9 clinical trials.¹ It is the only OTC laxative supported by both short-term and long-term clinical study data.

The 2023 AGA–ACG Guideline confirmed this with a strong recommendation with moderate certainty of evidence — making PEG the only OTC constipation treatment to receive a strong GRADE recommendation for chronic daily use.²

Pros and Cons

✅ Pros	❌ Cons
• Highest evidence grade (Grade A) • Only OTC laxative with long-term RCT data • Safe for daily chronic use • No dependency or tolerance risk • Tasteless; mixes into any drink	• Slow onset (24–72 hours) • Not suitable for urgent or immediate relief • May cause bloating or loose stools at high doses

Who Should Use It?

PEG is the best choice for people with chronic constipation — ongoing, recurring difficulty with bowel movements. It is also safe for elderly adults and pregnant women under physician guidance. See our full guide: Immediate Constipation Relief for Elderly Adults at Home.

📦 Our Pick: MiraLAX Laxative Powder — Unflavored, dissolvable in any beverage. Available in multiple sizes.
Onset: 24–72 hours | Use: Daily long-term | → Check Price on Amazon

2. Dulcolax (Bisacodyl) — Best for Rescue Relief

🏅 Evidence Rating: Grade B (2021) | Strong Recommendation for Short-Term Use (2023 AGA–ACG)

What Is It and How Does It Work?

Bisacodyl is a stimulant laxative that activates the muscles lining your intestines, triggering contractions and pushing stool through. According to Mayo Clinic, stimulant laxatives “trigger rhythmic contractions of intestinal muscles” to move stool along.³ It is available in both tablet and suppository form.

What Does the Research Say?

Bisacodyl and its close relative sodium picosulfate both received Grade B recommendations in the 2021 review — a significant upgrade from Grade C in the 2005 Ramkumar & Rao review.¹

The 2023 AGA–ACG Guideline issued a strong recommendation with moderate certainty of evidence for bisacodyl for short-term use (up to 4 weeks) or as rescue therapy.² This is notably stronger than the conditional recommendation given to senna under the same framework — which is why Bisacodyl ranks #2 overall despite its Grade B in the 2021 review.

Pros and Cons

✅ Pros	❌ Cons
• Strong 2023 AGA–ACG recommendation for short-term use • Evidence grade upgraded from C (2005) to B (2021) • Fast onset: 6–12 hrs oral; 15–60 min suppository • Available in tablets and suppositories	• Strong recommendation applies to short-term/rescue use only • High rate of cramping and diarrhea at initial doses • Not recommended for daily long-term use

📦 Our Pick: Dulcolax Stimulant Laxative Tablets — 5 mg bisacodyl tablets; also available as suppositories for faster action.
Onset: 6–12 hours (oral) | Use: Rescue/occasional | → Check Price on Amazon

3. Senokot (Senna) — Best Fast-Acting Natural Laxative

🏅 Evidence Rating: Grade A (2021) | Conditional Recommendation (2023 AGA–ACG)

What Is It and How Does It Work?

Senna is a plant-based stimulant laxative made from the leaves and pods of Senna alexandrina. Like bisacodyl, it stimulates muscle contractions in the intestines to move stool through the colon more quickly. According to Mayo Clinic, stimulants “trigger rhythmic contractions of intestinal muscles to eliminate stool.”³

What Does the Research Say?

In the 2021 systematic review, senna received a Grade A recommendation based on two clinical trials showing improved bowel movement frequency versus placebo.¹ However, one of those trials used higher doses than are standard in clinical practice — an important limitation to keep in mind.

The 2023 AGA–ACG Guideline gave senna a conditional recommendation with low certainty of evidence — weaker than both PEG and bisacodyl under the GRADE system.² This is why senna ranks #3, behind bisacodyl, despite sharing Grade A in the 2021 review.

Pros and Cons

✅ Pros	❌ Cons
• Grade A evidence in 2021 review • Fast relief — works in 6–12 hours • Natural plant-based origin • Affordable and widely available	• Conditional (not strong) 2023 recommendation • One key trial used above-standard doses • Not for daily long-term use • May cause cramping, urgency, and diarrhea • May cause harmless discoloration of urine

📦 Our Pick: Senokot Natural Vegetable Laxative — Standardized senna, available in tablets and liquid form.
Onset: 6–12 hours | Use: Short-term/occasional | → Check Price on Amazon

4. Metamucil (Psyllium Husk) — Best for Daily Fiber Support

🌿 Evidence Rating: Grade B (2021) | Conditional Recommendation (2023 AGA–ACG)

What Is It and How Does It Work?

Metamucil contains psyllium husk, a soluble fiber derived from the seeds of Plantago ovata. According to Mayo Clinic, bulk-forming laxatives like Metamucil “absorb water to form soft, bulky stool, prompting normal contraction of intestinal muscles.”³ It is the gentlest laxative type and the only one that closely mimics natural bowel function.

What Does the Research Say?

Psyllium received a Grade B recommendation in the 2021 systematic review.¹ It is important to be transparent about the evidence: two placebo-controlled trials found psyllium was no better than placebo for improving overall constipation symptom scores, and it performed less effectively than mangoes and prunes in direct comparisons.

Despite this, psyllium earned Grade B because it reliably improves stool bulk and consistency, has an excellent long-term safety record, and offers additional health benefits — including lowering LDL cholesterol and supporting blood sugar control. The 2023 AGA–ACG Guideline recommends psyllium as a conditional first-line therapy, especially for people with low dietary fiber intake.² Mayo Clinic describes fiber supplements as “the gentlest on your body.”³

For a complete comparison of all fiber supplement options, see our guide: 7 Natural Fiber Supplements for Chronic Constipation.

Pros and Cons

✅ Pros	❌ Cons
• Safe for daily long-term use • Also lowers LDL cholesterol and supports blood sugar control • Gentle; suitable for pregnancy and elderly adults • Supports gut microbiome health • No dependency risk	• Grade B (moderate, not strong evidence) • Slower onset than PEG or stimulant laxatives • No benefit over placebo in 2 clinical trials • Less effective than mangoes and prunes in direct comparisons • Must be taken with plenty of water to avoid choking risk

📦 Our Pick: Metamucil Psyllium Fiber Supplement — Available in powder, capsules, and wafers. Orange flavor or unflavored.
Onset: 12–72 hours | Use: Daily long-term | → Check Price on Amazon

5. Magnesium-Based Laxatives — Best for Gentle Overnight Relief

🌿 Evidence Rating: Grade B — magnesium salts collectively (2021) | Conditional, Very Low Certainty for Magnesium Oxide (2023 AGA–ACG)

What Are They and How Do They Work?

Magnesium laxatives work by drawing water into the colon through an osmotic effect. Mayo Clinic lists Milk of Magnesia (magnesium hydroxide) alongside PEG in the “oral osmotics” category.³ There are three common forms:

• Magnesium oxide — tablet form; the primary form studied in clinical trials
• Magnesium citrate — liquid form; fastest onset (30 min–6 hours). Note: not separately graded in the 2021 review; evidence is extrapolated from magnesium salts as a group
• Magnesium hydroxide (Milk of Magnesia) — liquid suspension; the classic gentle option

What Does the Research Say?

Magnesium salts as a group received a Grade B recommendation in the 2021 review, based primarily on trials of magnesium oxide.¹ Magnesium oxide outperformed placebo and was found non-inferior to senna in one qualifying trial. The 2023 AGA–ACG Guideline gave magnesium oxide a conditional recommendation with very low certainty of evidence — the lowest certainty rating among all evaluated agents.²

For a detailed comparison of specific magnesium products, see our guide: 5 Best Magnesium Supplements for Constipation.

Pros and Cons

✅ Pros	❌ Cons
• Grade B evidence for magnesium salts collectively • Magnesium citrate: very fast onset (30 min–6 hrs) • Non-stimulant; gentle on the gut • Multiple forms available (tablet, liquid, suspension)	• Magnesium oxide: very low certainty in 2023 guideline • Magnesium citrate not separately graded in clinical reviews • Contraindicated in kidney disease • Risk of diarrhea or electrolyte imbalance if overused • Efficacy varies between different magnesium forms

📦 Milk of Magnesia: Phillips’ Milk of Magnesia — Gentle overnight relief. Available in original and mint flavor.
Onset: 6–12 hours | → Check Price on Amazon

📦 Magnesium Citrate: Magnesium Citrate Liquid — Fastest-acting magnesium option.
Onset: 30 min–6 hours | → Check Price on Amazon

6. Kiwi & Prunes — Best Natural Food-Based Options

🍏 Evidence Rating: Grade B — kiwi, prunes, mango, and figs (Rao & Brenner 2021)

Research has found that certain fruits act as effective natural laxatives. The 2021 systematic review gave Grade B recommendations to four fruit-based options: kiwi, prunes (dried plums), mango, and figs.¹ These fruits contain fiber, sorbitol, and natural sugars that help retain water in the colon and stimulate bowel movements.

• Kiwi — supported by two clinical trials in the 2021 review; the strongest fruit-based evidence overall
• Prunes — supported by one clinical trial; in a direct comparison study, prunes outperformed psyllium for stool frequency
• Mango and figs — each supported by a single study; both received Grade B

Notably, the 2021 review found that psyllium was less effective than mangoes and prunes in direct comparisons — meaning these natural food options can genuinely outperform a commonly recommended fiber supplement.¹

For more on fiber-rich foods that support bowel health, see our guide: Best Fiber Foods and Fiber Therapy for Gut Health.

7. Colace (Docusate) — Verdict: Not Recommended for Constipation

❌ Evidence Rating: Grade I — Insufficient Evidence (2021) | No Recommendation Issued (2023 AGA–ACG)

Docusate sodium (sold as Colace and Dulcolax Stool Softener) is one of the most widely purchased stool softeners in the US. It works by reducing the surface tension of stool, theoretically allowing water and fats to penetrate and soften it from within.

However, the clinical evidence does not support its use for constipation. The 2021 systematic review assigned docusate Grade I (insufficient evidence) — meaning there is not enough quality data to make any recommendation.¹ The 2023 AGA–ACG Guideline issued no recommendation for it. Mayo Clinic states there is “no evidence that they improve symptoms” of constipation in controlled clinical trials.³

One important nuance: Docusate is still commonly used for post-surgical patients and new mothers to reduce straining — not to treat constipation directly, but to prevent discomfort from straining after procedures or childbirth. In that specific clinical context, it may still be appropriate when directed by a physician. For constipation relief, however, PEG or psyllium are significantly better-supported alternatives.

Safety, Side Effects, and Drug Interactions

Across all 41 trials included in the 2021 review, no serious adverse events were reported for any OTC laxative.¹ Common side effects — bloating, cramping, gas, and loose stools — are mild and typically dose-dependent.

However, Mayo Clinic warns that overuse of laxatives can lead to serious health problems, including electrolyte imbalances that affect the heart, muscles, and nervous system.³

Key safety guidelines by product type:

• Stimulant laxatives (senna, bisacodyl): Do not use daily long-term without a doctor’s guidance. Effective short-term; risk of dependency with chronic overuse.
• Magnesium laxatives: Avoid entirely if you have kidney disease — see the kidney warning in Section 5 above.
• All laxatives: Always drink plenty of water. Dehydration worsens constipation and can amplify side effects. See: Does Dehydration Cause Constipation?
• Drug interactions: Oral laxatives can reduce the absorption of certain antibiotics, heart medications, and bone density medications. Do not take other medications within 2 hours of a laxative dose unless directed by a physician.

Special Populations: Who Needs Extra Care

• Elderly adults: More prone to side effects and drug interactions. PEG is the preferred first choice. See: Immediate Constipation Relief for Elderly Adults at Home
• Pregnant women: Psyllium and PEG are generally considered the safest OTC options, but always consult your doctor before use. Stimulant laxatives should be avoided unless specifically prescribed. For pregnancy-related guidance, see: High-Fiber Foods for Pregnancy Constipation
• Hemorrhoid patients: Prefer PEG or psyllium to avoid straining, which can worsen hemorrhoids.
• Kidney disease patients: Avoid all magnesium-based laxatives due to risk of hypermagnesemia.
• Children: Always consult your child’s doctor before giving any laxative. Dosing guidelines differ significantly from those for adults.

When to See a Doctor — Do Not Ignore These Signs

Mayo Clinic advises contacting your healthcare provider promptly if you experience any of the following:³

• Severe stomach cramps or pain
• Unexplained changes in bowel patterns lasting more than 2 weeks
• Constipation that persists longer than 7 days despite laxative use
• Blood in your stool or rectal bleeding
• Unexplained weight loss
• Unusual weakness or fatigue

These symptoms may indicate a more serious underlying condition — not simply a need for a stronger laxative. Constipation can sometimes be a sign of hypothyroidism, irritable bowel syndrome (IBS), colon obstruction, diabetes, or other conditions that require proper medical diagnosis and treatment.

Frequently Asked Questions

Final Recommendation: Which One Should You Choose?

After reviewing the 2021 Rao & Brenner systematic review, the 2023 AGA–ACG Clinical Practice Guideline, and Mayo Clinic guidance, here is the complete evidence-based ranking:

• For chronic constipation (daily use): Start with MiraLAX (PEG) — Grade A, strong recommendation, the only OTC laxative proven safe and effective for long-term daily use.
• For rescue or occasional fast relief: Use Dulcolax (Bisacodyl) — strong 2023 recommendation for short-term use; fastest oral onset among strongly-recommended options.
• For a fast-acting natural option (short-term): Senokot (Senna) — Grade A in 2021, but conditional recommendation in 2023; use sparingly and not daily long-term.
• For daily fiber support and overall health: Metamucil (Psyllium) — Grade B; best for people who also want benefits for cholesterol and blood sugar alongside constipation support.
• For gentle overnight relief: Milk of Magnesia or Magnesium Citrate — Grade B; avoid entirely if you have kidney disease.
• For a food-first approach: Prunes and kiwi — Grade B; prunes outperformed psyllium in a head-to-head comparison.
• Avoid for constipation: Colace (Docusate) — Grade I; no clinical evidence it works for constipation.

For most adults with chronic constipation, starting with PEG combined with key lifestyle changes — drinking 8–10 glasses of water daily, consuming 25–31 grams of dietary fiber, and exercising regularly — gives you the strongest evidence-backed approach available without a prescription.

For additional natural options to use alongside or before laxatives, see: Natural Constipation Relief: 7 Best Remedies.

References

1. Rao SSC, Brenner DM. Efficacy and Safety of Over-the-Counter Therapies for Chronic Constipation: An Updated Systematic Review. Am J Gastroenterol. 2021;116(6):1156–1181. https://doi.org/10.14309/ajg.0000000000001222
2. Lacy BE, et al. AGA–ACG Joint Clinical Practice Guideline on the Management of Chronic Idiopathic Constipation. Gastroenterology. 2023. https://doi.org/10.1053/j.gastro.2023.03.214
3. Mayo Clinic. Laxatives: OTC products for constipation. https://www.mayoclinic.org/diseases-conditions/constipation/in-depth/laxatives/art-20045906